Influenced by divorce statistics, two-career households, rapidly changing parenting roles, and most recently by family theory and therapy, child development research began a systematic examination of the ways in which different family subsystems (i.e. mother-child, father-child, husband- wife) contributed to the growth or hinderance of children's adaptive skills, socioemotional development, and relationships outside the home. Although the inclusion of different family dyads in studies of child development represented a major shift from the traditional focus on mothers, research continued - and continues - to neglect an important dimension of the family's emotional life -relational dynamics taking place at the level of the whole family' group. This is a significant oversight, since such dynamics provide family members with unique and powerful information about how relationships work. The proposed study takes as its focus several key but understudied aspects of co-parenting and family-level behavior, examining the degree to which a family group level of analysis contributes to the understanding of several key socioemotional indices in 2 1/2 year old children. Guiding the investigation are two major questions: (1) Do individual differences in family-group dynamics provide unique information toward predicting important child developmental indices during toddlerhood, beyond variability accounted for by the field's more traditional markers of attachment security and marital distress? (2) Are co-parenting and family-level dynamics a mechanism through which marital distress comes to affect child developmental outcomes? To examine these questions, 70 couples, recruited from Worcester-area toddler and daycare centers, will be studied as they participate in laboratory-based family interaction sessions with their 30-month-old sons or daughters. Independent laboratory assessments will examine: (a) each parent-child relationship; (b) the marital relationship; (c) interactions taking place at the level of the whole family group; and (d) toddlers' ego development, understanding of emotions, and emerging ideas about relationship. Both parents and daycare center directors will provide additional assessments of children's behavioral and emotional adaptation. Paper-and- pencil measures of child temperament and of individual, marital and family functioning will also be gathered. Regression analyses will examine whether co-parenting and family variables (e.g. hostility-competitiveness, family harmony, parenting discrepancies) contribute uniquely to the prediction of socioemotional development, beyond the contributions of parent-child attachment and marital distress. Latent variable path analysis with partial least squares examination procedures will examine direct (marriage-to-child) vs indirect (marriage-family-child) models.